1. Field of the Invention
The present invention relates to a thin film transistor (TFT), and more particularly, to a TFT that has an efficient layout, a fabrication method thereof, a liquid crystal display (LCD) device having the TFT, and a fabrication method thereof.
2. Discussion of the Related Art
An LCD device is spot-lighted as a next-generation display device of light weight, slim profile, and low power consumption that is convenient to carry with, technology-concentrated, and a high value-added product.
With liquid crystal (LC) interposed between two substrates, the LCD device displays a predetermined image using a difference in refractive index of light due to anisotropy of the LC.
An active matrix liquid crystal display (AMLCD) device in which TFTs and pixel electrodes are arranged in a matrix has excellent resolution and an excellent moving-image realization capability, and thus is becoming more prevalent in the market.
FIG. 1 is a schematic view illustrating the related art LCD device.
As illustrated in FIG. 1, driver integrated circuits (ICs) 108 and 112 are mounted in a tape automated bonding (TAB) type. That is, gate driver ICs 112 are mounted on gate tape carrier packages (TCPs) 114 and data driver ICs 108 are mounted on data TCPs 110.
A gate printed circuit board (PCB) 104 is connected with an LC panel 102 by the gate TCP 114 and a data PCB 106 is connected with the LC panel 102 by the data TCP 110.
The data PCB 106 generates a data control signal for controlling the data driver IC 108 and supplies the data control signal and predetermined video data to the data driver IC 108. For that purpose, the data PCB 106 has a signal pad 118. The signal pad is a terminal for receiving video data and vertical/horizontal synchronization signals (Vsync, Hsync) from an outside. The data control signal is generated by the Vsync and Hsync.
The data PCB 106 is electrically connected with the gate PCB 104 by a flexible printed circuit (FPC) 116.
The gate PCB 104 generates a gate control signal for controlling the gate driver IC 112 using Vsync/Hsync signals inputted from the signal pad 118 of the data PCB 106 to supply the generated gate control signal to the gate driver IC 112.
As described above, because the gate PCB and the data PCB are separately provided in the related art LCD device and because the gate driver IC and the data driver IC are a chip that must be mounted on the TCP separately, the number of parts in the display increases, manufacturing costs increase, and the process becomes more complicated.
In the related art LCD device, as resolution increases, the size of the pitch of a pad connecting the TCP with gate lines or data lines decreases, causing a problem in that bonding between a TCP metal line and the pad is not easy achieved.
Therefore, technology for mounting a driver circuit for driving an LC panel in the inside of the LC panel has been developed.
The driver circuit has a plurality of TFTs. For example, a gate driver mounted within the LC panel has a plurality of shift registers and a plurality of TFTs for controlling respective outputs of the shift registers.
In this case, for the driver circuit to be reliable, each TFT should have an exact and swift switching function. For that purpose, the TFT should have good charge mobility and a good current-driving ability. To meet these requirements, a channel of the TFT should be widened as much as possible.
However, when the channel width of the TFT is widened, because the area occupied by the driver circuit becomes large and the size of a bezel area at the outer edge of a screen becomes large, a screen's display area is reduced. Therefore, to secure a screen of the same size, the size of the LC panel should increase.